The sandbox property of an iframe improves web page security by restricting the permissions of embedded content. Its core function is to prevent the content in the iframe from performing operations such as accessing cookies, executing scripts, etc., and the usage method is to add sandbox attributes, such as <iframe src="example.html" sandbox></iframe>. Optional values include allow-same-origin, allow-scripts, allow-forms, etc., which are used to open permissions on demand, such as allowing scripts and forms to be submitted but prohibiting pop-ups: sandbox="allow-scripts allow-forms". Recommended usage includes configuring reasonable permissions based on content type, such as ad space recommendations allow-scripts and allow-forms, and gadget recommendations plus allow-same-origin. At the same time, it is necessary to note that sandbox should not be used as the only security line. It also needs to combine CSRF protection, input filtering and other measures to test browser compatibility. In short, using sandbox rationally can effectively reduce the risk of XSS and click hijacking.
The sandbox
attribute of iframe
is a practical tool to improve web page security. It prevents malicious content from performing dangerous actions by restricting the behavior of embedded pages. This attribute is very useful if you want to control your third-party content or ads when using them.

Basic function: Restrict the permissions of content in iframes
By default, content in iframe
may have the same security permissions as the main page, such as accessing cookies, executing scripts, submitting forms, etc. After adding the sandbox
attribute, the browser will restrict these behaviors.
You can use this:

<iframe src="example.html" sandbox></iframe>
As long as this attribute is added, the content in the iframe will be "sandboxed" - even if it comes from a homologous or untrusted source, the page cannot be operated at will.
Optional value: Open permissions on demand
sandbox
attribute is not either on or off. It supports multiple optional values to gradually release certain permissions. Common ones include:

-
allow-same-origin
: Allows iframe content to be treated as the same origin as the main page (otherwise it will be processed as passive content) -
allow-scripts
: allows script execution -
allow-forms
: Allow submission of forms -
allow-popups
: Allow popups -
allow-downloads
: Allow downloads to download files -
allow-pointer-lock
: Allows the use of Pointer Lock API (for games, etc.)
For example, if you want to allow scripts to run and form submission, but disable popups:
<iframe src="example.html" sandbox="allow-scripts allow-forms"></iframe>
Note: Without
allow-same-origin
, the content in the iframe will not be accessible to cookies or local storage, which is a very critical security guarantee in some scenarios.
Use suggestions: Set reasonable permissions based on content type
When using sandbox
, the most important thing is to minimize authorization , that is, only give the function permissions required by the iframe. The following are the recommended configurations for several common scenarios:
Advertising space : Usually, you do not need to access the main page information or pop-up windows. You can only allow scripts and forms:
sandbox="allow-scripts allow-forms"
Embed external widget : If it depends on a homologous context (such as login status), you need to add
allow-same-origin
:sandbox="allow-scripts allow-same-origin"
Content that is totally trusted : This is less case, but it is still recommended to keep some restrictions for increased security.
- Don't fully trust content provided by users;
- CSRF protection is still required for sensitive operations;
- Input filtering and permission control should also be done on the server side.
Security reminder: Don't rely on sandbox as the only line of defense
Although sandbox
is a powerful security mechanism, it cannot replace other security measures. for example:
In addition, different browsers have slightly different support for sandbox
, especially some older browsers may not support certain options. It is best to test whether the behaviors in mainstream browsers are consistent before going online.
Basically that's it. Using sandbox
well can effectively reduce the risks of XSS and click hijacking without affecting the functional experience.
The above is the detailed content of HTML `iframe` Sandbox Attribute Explained. For more information, please follow other related articles on the PHP Chinese website!

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